This invention is in the general field of surgical instruments. It relates specifically to catheters which may be used in cardiovascular and endovascular procedures to deliver diagnostic, therapeutic, or vaso-occlusive agents or devices to a target site within a human or animal body which is accessible by a system of natural passageways within that body. The catheters are coated in such a way that they are exceptionally slippery and the coating is very durable. The invention also relates to methods for coating the catheters and to methods for applying lubricious coatings.
Catheters are increasingly used to deliver diagnostic or therapeutic agents and devices to internal target sites that can be accessed through the circulatory or other system. There are a number of general approaches for placing catheters within vessels in the body to reach target sites that are difficult to access. In one technique, a torqueable guidewire is introduced into the vasculature and, using radiography to monitor its advance through the body""s passageways, is rotated to allow the guidewire""s bent guide tip to follow a chosen route (when a choice of pathways is found) and advanced towards the target site. At chosen intervals during the guidewire""s advancement, the catheter is slid along the guidewire until the distal end of the catheter approaches the distal end of the guidewire. This procedure is repeated until the distal end of the catheter is positioned at the target site. An example of this technique is described in U.S. Pat. No. 4,884,579. This is a widely accepted and respected method for approaching target sites in complicated area of the vasculature. It, however, has the drawback of being somewhat time-consuming due to the necessity of rotating and advancing the guidewire and catheter through the vasculature.
A second technique for advancing a catheter to a target site is to use the blood flow as the motive force in placing the distal end of the catheter at the desired target site. Such methods often employ a highly flexible catheter having an inflatable, but pre-punctured balloon at its distal end. In use, the balloon is partially inflated, and carried by blood flow into the target site. During placement, the balloon is continually inflated to replenish fluid leaking from the balloon. This technique, too, has drawbacks including the fact that at least the distal portion of the catheter is so floppy that it cannot be pushed without buckling. Instead the catheter must be advanced using injected fluid to inflate the balloon to propel the catheter to the target site. Additionally, there is a risk of rupture of a vessel by a balloon that has been overinflated.
In order to address some of the above described problems, another approach has involved the use of flexible catheters having extremely flexible distal portions which can be directed to a target site using the blood flowing to that site as the motive force but without the use of balloons on the distal catheter tip. These flow-directed catheters have the advantage of being quite fast in that they are able to access remote portions of the body very quickly. They carry the obvious limitation that the catheter distal tip can only go where the blood flow is the highest. Furthermore, the catheters often are limited in the size of the xe2x80x9cloadxe2x80x9d carried to the selected site. Said another way, balloon-less flow-directed catheters may be a marginal choice if a larger embolic coil or large diameter particle is to be delivered to the select site. One aspect of this invention involves the coating of catheters such as these to further improve their access rate.
On the other hand, over-the-wire catheters having variable stiffness, although quite strong and able to deliver embolic coils and large diameter particles through their large lumen, are comparatively quite slow in time of access. Friction with the interior of the guide catheter or the vessel path considerably slows the procedure time. However, the over-the-wire catheters can be directed to portions of the vasculature inaccessible to the flow-directed catheter. Lowering the resistance of the over-the-wire catheter to improve its lubricity and allow improved access time to remote body sites forms a further aspect of this invention.
This invention is generically a coated catheter having portions of differing flexibility which is suitable for the delivery of diagnostic, therapeutic, or vaso-occlusive agents or devices to potentially remote portions of the vascular system or other systems of open lumen within the body. The coating is significantly slipperier than other known coatings and is very durable.
This invention also includes a method of coating catheters using lubricious hydrophilic polymers and a method for producing a thin layer of such polymers on polymeric substrates.
The invention also includes a method for placing the catheter at the target site and a method for delivering diagnostic, therapeutic, or vaso-occlusive agents or devices to the target site.
This invention is a coated catheter for placement within a tortuous, small vessel pathway and a method for delivery of an agent or device to a target site. The coating is very slippery and quite durable. The catheter may be directed to the target site either by means of the blood flow to that site or by the use of a guidewire. The catheter has an elongate tubular body having proximal and distal ends and a lumen extending between the ends through which the diagnostic, therapeutic, or vaso-occlusive agent or device is delivered. Where appropriate, the lumen may be used for passage of a guidewire.
The elongate tubular body typically is formed of (a) a relatively stiff and, perhaps, tapered proximal segment, (b) a relatively flexible distal segment, and (c) a transition or intermediate section between the proximal and distal segments that is less flexible than the distal segment but more flexible than the proximal segment. At least the distal segment and, desirably, the transition segment of the catheter is treated with a lubricious, polymeric material. If so desired, all but the portion of the proximal section actually handled by the physician during final manipulation may be coated with the lubricious polymers.
The catheter bodies are coated with hydrophilic polymeric materials by a method involving application of the polymer from a dilute polymer or oligomer solution followed by simultaneous solvent removal and curing of the applied precursor. Multiple coatings of the polymeric material are contemplated.